Burner for heating a gaseous medium having a low oxygen content



Feb. 10, 1970 L. s. SPIELMAN 3,494,711

BURNER FOR HEATING A GASEOUS MEDIUM HAVING A LOW OXYGEN CONTENT Filed June 28, 1968 3 Sheets-Sheet 1 INVENTOR F I 6. 2 /EL MAN Arrorn ey Feb-10, L. S. SPIELMAN BURNER FOR HEATING A GASEOUS MEDIUM HAVING A LOW OXYGEN CONTENT Filed June 28. 1968 5 Sheets-Sheet 2 INVENTOR LYLE S. S LMAN FIG. 4 By A Horney Feb -10, 1970 s. SPlELMAN BURNER FOR HEATING A GASEOUS MEDIUM HAVING A LOW OXYGEN CONTENT 3 Sheets-Sheet 5 Filed June 28, 1968 FIG. 7

FIG. 6'

/NVEN7'0/? LYLE 8, 5 lELMA/V M A Horney United States Patent 3,494,711 BURNER FOR HEATING A GASEOUS MEDIUM HAVING A LOW OXYGEN CONTENT Lyle S. Spielman, Rockford, Ill., assignor to Eclipse Fuel Engineering Co., Rockford, 11]., a corporation of Illinois Filed June 28, 1968, Ser. No. 741,085 Int. Cl. F23d 11/42 U.S. Cl. 431-165 Claims ABSTRACT OF THE DISCLOSURE A gas burner adapted primarily for positioning in a moving gaseous medium having a low oxygen content. A tubular burner body presents a forward burner face directed downstream and has a multiplicity of small fuel and air ports. A sheet metal shroud encompasses the burner body and establishes a fresh air manifold and a combustion trough forwardly of the fuel and air ports. The manifold feeds make-up or maintenance air to the flame at the base of the trough while the gaseous medium of low oxygen content is fed to the trough further downstream under the impetus of such gaseous medium flowing past the burner. Some maintenance air is fed from the manifold to the trough at a region immediately preceding the region of introduction of the gaseous medium of low oxygen content to the trough.

The present invention relates to a gas burner of the general type which is shown and described in U.S. Reissue Patent No. 26,244, granted on Aug. 1, 1967 and entitled Air Heating Burners, the present burner being an improvement over those of said patent and characterized by the fact that it will operate efficiently in a moving gaseous medium having a low oxygen content.

A gas burner of the general type under consideration is adapted to be positioned in a moving gaseous medium for the purpose of heating the gaseous medium which flows past it, the burner relying, at least in part, for its operation upon any small amount of oxygen in the gaseous medium, together with a supply of fresh air in suflicient quantity to maintain combustion. Some such burners receive their fresh air by using premixed gas and air while others are of the mixing type in that the fresh air that is supplied thereto is mixed with the gaseous fuel in the combustion chambers of the burners. It is to this latter class or type of gas burners that the present invention specifically pertains.

Heretofore, the design of a gas burner which utilizes oxygen from the moving gaseous medium in which it is disposed is such that the minimum oxygen content in the gaseous medium may not drop below approximately 16% without danger of flame extinction or extreme burner inefficiency. Where the oxygen content is less than this, fresh air must be supplied from an outside source in order to support combustion under all conditions in which the burner may be used. For example, a burner of the type which is illustrated and described in aforementioned Reissue Patent No. 26,244 is designed to use approximately 16,000 cubic feet of air per hour for each lineal foot of the burner body when the oxygen content of the gaseous medium flowing past the burner drops to low minimal levels. The burner of the present invention is designed to operate at such low levels of oxygen content in the gaseous medium flowing past the same with an appreciable reduction in the quantity of fresh outside air that is supplied thereto, and the principal object of the invention is the provision of such a burner.

The attainment of this object is made possible by providing a novel burner body and sheet metal shroud assembly, the burner body remaining substantially the same as that of aforementioned Reissue Patent No.

r. CC

which issues from the burner body at the base of the trough. The manifold feeds make-up or maintenance air to the flame at the base of the combustion trough while the gaseous medium of low oxygen content is fed to the trough further downstream under the impetus of such medium flowing past the burner. Some maintenance or make-up air is fed from the manifold to the trough at a region immediately preceding the region of introduction of the gaseous medium and forwardly of the region of fresh air supply.

Apart from the reduction in the amount of fresh air which is supplied to the burner from an outside source, the general objects of the present invention remain substantially the same as those expressed in the heretofore mentioned reissue patent.

Other objects and advantages of the invention will readily suggest themselves as the nature of the invention is better understood from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by the claims at the conclusion hereof.

In the accompanying three sheets of drawings forming a part of this specification or disclosure, one illustrative embodiment of the invention is disclosed although numerous other embodiments are contemplated.

In these drawings:

FIG. 1 is a top plan view of a composite sectional burner constructed according to the present invention and showing the same operatively installed in a stream of a gaseous medium such, for example, as recirculated air, the duct for the stream being shown in horizontal section;

FIG. 2 is a front elevational view of a complete burner section, illustrating the manner in which it is joined to an adjacent and similar section;

FIG. 3 is a transverse sectional view taken substantially on the line 33 of FIG. 2;

FIG. 4 is a longitudinal sectional view taken substantially on the line 44 of FIG. 2 with certain portions of the sheet metal shroud assembly being broken away in order more clearly to reveal the nature of the invention;

FIG. 5 is a perspective view of the burner casting or body with the sheet metal shroud assembly removed therefrom;

FIG. 6 is a plan View of an end closure plate for the burner casting or body of FIG. 5;

FIG. 7 is a plan view of a gas-admission end plate for the burner casting or body of FIG. 5; and

FIG. 8 is an enlarged sectional view taken substantially on the line 8-8 of FIG. 3.

Referring now to the drawings in detail and in particular to FIG. 1, an assembled sectional gas burner 10 embodying the present invention is shown as being transversely arranged in a stream (indicated by the arrow) of a gaseous medium of low oxygen content, the stream being confined in a duct 12. While the present burner 'will operate satisfactorily in a fresh air stream, for purposes of discussion herein, the stream is considered to be a gaseous medium of low oxygen content such, for example, as a continuously recirculating air stream, the percentage of oxygen contained therein being a function of the amount of fresh air that is brought into the system and the amount of air that is used by the burner, it being understood that the burner 10 relies for its operation upon oxygen which is Withdrawn from the gaseous medium or air stream each time it passes the burner, as Well as upon the introduction thereto of a small amount of fresh make-up or replacement air from an outside source which is fed thereto to compensate for the burned oxygen and to maintain the required oxygen level to support combustion. The stream may be associated with the recirculating duct work of an industrial oven or the like. The gaseous medium or recirculated air stream may be impelled through the duct 12 by means of a suitable motor-driven blower (not shown) and the burner 10 may be disposed on either the suction or the pressure side of such blower.

The burner 10 involves in its general organization a burner proper 20 which comprises a plurality of longitudinally aligned individual burner-bodies 22, the latter being preferably in the form of castings (see FIG. The burner bodies are bolted together in a manner that will be made clear subsequently in order to establish the burner proper 20. The latter has associated therewith an assembly of sheet metal work which establishes for each burner body two chambers 24 (see FIG. 3) for receiving portions of the moving gaseous medium and, in addition, a fresh air supply manifold 26 which substantially encompasses the upper, lower, and rear sides of the burner proper as it is viewed in FIG. 1.

Although in FIG. 1, as in most normal gas burner installations, the burner proper 20 is placed on its side so that the front of the burner extends in the direction of flow of the gaseous medium and towards the downstream side thereof, in FIG. 3 the burner proper 20 is shown as facing upwardly and in the following description (except where reference to FIG. 1 is specifically made) as well as in the appended claims, reference to the burner proper, together with its associated assembly of sheet metal work and apart from the moving gaseous medium in which it is mounted, will be made on the basis of such orientation.

As best illustrated in FIGS. 3 and 5, each burner body 22 of the burner proper 20 is of elongated open-ended tubular design and includes a bottom wall 30, a pair of spaced apart side walls 32, and a centrally and longitudinally divided top wall 34, the latter having inclined side portions which slope upwardly and inwardly at a small angle. The interior of the burner body establishes a straight longitudinally extending passageway and it provides an elongated gas chamber 36. The forward region of the burner body is undercut as indicated at 35 in order to provide a hollow centrally disposed on the top wall 34 a longitudinally extending web 38 which serves to support a substantially flat but relatively thick burner head 40, the latter being formed with a rectilinear series. of relatively small, closely spaced, upwardly extending burner gas ports 42. The latter communicate with the gas chamber 36 through the hollow web 38. The ports 42 are disposed in a longitudinal row along the burner head medially between the side edges thereof. The side regions of the burner head 40 establish flanges 43 which overlie the top wall 34 of the burner body as best seen in FIG. 3 and are provided with respective rows of spaced apart fresh air ports 44, the nature and function of which will be set forth presently. The fresh air ports 44, as well as the gas ports 42, extend from the undercut portions 35 and open forwardly onto a flat burner face 46. In addition, they lead to and communicate with a V-shaped combustion trough 48 which is defined by the '52 therein for reception of clamping bolts 54.

The sheet metal work assembly which is associated with each burner body 22 is in the form of a burner shroud and is of a composite nature. The chambers 24 on opposite sides of each burner body are defined by two flameconfining walls 56 which may extend upwardly and outwardly and have an included angle of approximately 26, and define the aforementioned combustion trough 48, the distal or upper portions of these Walls constituting the inner side walls of the chambers 24. If desired, however, the walls 56 may be parallel to one another. The proximate or lower edges of the walls 56 are secured to the sides of the burner head 40 by bolts 58 which extend into tapped holes in the head. The distal or upper edges of the walls 56 are turned laterally outwards and provide top walls 60 for the chambers 24. The outer edges of these top walls are secured to the upper edges of the outer rectangular side walls 64 of the chambers 24. The lower edges of the side walls 64 are bent or turned inwardly to provide bottom walls 66 for said chambers, and the inner edges of the bottom walls 66 merge with rectangular vertical walls 68 which, in the main, constitute the outer side walls of the aforementioned burnerencircling fresh air supply manifold 26. The lower edges of the vertical walls 68 are connected by a horizontal Wall 70 which, in effect, constitutes a supporting plate by means of which the sheet metal shroud, in the main, is secured to the burner body, fastening bolts 71 serving to secure this plate to the botom wall 30 of the burner body. A rectangular sectional box-like structure including side walls 72 and a bottom wall 74 underlies the bottom wall 30 of the burner body 22, has its bottom wall spaced from the burner body and its side Walls forming a continuation of the vertical Walls 68, while the bottom wall 74 also constitutes the bottom wall for the burner-encircling fresh air supply manifold 26. A reinforced fresh air entrance opening 76 is formed in the bottom wall 74. The top wall of the fresh air supply manifold 26 is established by a pair of elongated sheet metal strips 78 which extend between the upwardly and outwardly inclined flame-confining walls 56 and the upper portions of the vertical walls 68 and thus divide or separate the burnerencircling fresh air supply manifold from the recirculated air supply chambers 24.

It is to be noted that the vertical walls 68 are spaced from the side walls 32 of the burner body 22 so that the side portions of the horizontal wall 70 overhang the bottom side edges of the burner body, as clearly illustrated in both FIGS. 3 and 8. These overhanging side portions of the horizontal wall 70 are formed with relatively 0 large slot-like ports 80 in order that the fresh air which is introduced into the box-like lower region of the fresh air supply manifold 26 flows upwardly around the sides of the burner body and from thence into the upper region of the interior of the manifold 26, the latter being defined by the strips 78, the vertical walls 68 and portions of the upwardly and outwardly inclined flame-confining walls 56. The slot-like ports 80 oifer little resistance to air flow therethrough and, consequently, the interior of the fresh air supply mainfold 26 may be considered to embody three major portions, namely, a lower portion 26a beneath the burner body 22, a medial divided portion 26b on oppo site sides of the burner body, and a divided upper portion 260 immediately about the top wall 34 of the burner body.

The fresh air supply manifold 26 communicates with the combustion trough 48 by means of longitudinal series of fresh air outlet ports 82 in the proximate or lower regions of the outwardly and upwardly inclined flameconfining walls 56. Such ports are disposed a slight distance below the strips 78, while the interiors of the chambers 24 communicate with the combustion trough 48 through vertically spaced longitudinal series of outlet ports 84 which are formed in distal regions of the flame-confining walls 56 and are located above the level of the strips 78. A single longitudinal series of inlet ports 86 is formed in each of the bottom walls 66 of the chambers 24, and since these bottom walls extend tranversely of the moving gaseous medium within which the burner is disposed, portions of the gaseous medium are constrained or caused to enter the chambers 24 at all times. Additional longitudinal series of outlet ports 88 are formed in the top Walls 60 of the chamber 24 for the discharge of portions of the gaseous medium into the stream at a region just beyond the mouth of the combustion trough 48. Preferably, each top wall 60 has but a single series of outlet ports 88.

The specific size, number, and disposition of the various ports 80, 82, 84, 86 and 88 may be varied within certain tolerable limits. However, in the illustrated form of the invention, the fresh air outlet ports 82 in each forwardly and outwardly inclined flame-confining wall 56 are arranged in a single longitudinal row or series, while the ports 84 in each Wall 56 are arranged in three vertically spaced rows so that these latter ports are widely distributed over the areas of the walls 56 above the level of the strips 78. The ports 86, as well as the ports 88, are disposed in single longitudinal rows or series as shown in FIG. 1.

Means are provided whereby the various sheet metal components of the burners proper 20 may be secured together in end-to-end relationship to establish continuity of the aligned chambers 24 and the aligned fresh air supply manifolds 26. Accordingly, laterally and outwardly extending attachment or bolting flanges 90 are formed along the end edges of certain of the sheet metal components of the burner shroud assemblies. Abutting or adjacent bolting flanges are secured together in face-to-face relationship by means of fasteners, such, for example, as fastening bolt and nut assemblies 92. The normally open ends of the chambers 24 and the fresh air supply manifolds are closed by sheet metal plates 93 which are appropriately or suitably connected to the various walls 60, 64, 66, 68 and 74.

It is to be noted that although the effective outlines of the various sheet metal components which establish the chambers 24 and the manifold chamber 26 of each burner proper 20 have been described with reasonable particularity, the attachment means whereby these components are fastened together have not been described since the sheet metal Work that is involved in preparing these components may vary to a considerable degree. In general, it is deemed suflicient to state that lateral attachment flanges such as are shown at 94 and of any desired extent may be provided along the longitudinal edges of certain of the sheet metal walls and bolted to the longitudinal edge regions of adjacent sheet metal walls wherever right angle corners are to be established. In the case of the aforementioned box-like structure beneath the bottom wall 30 of the burner body 22, small attachment ears 96 may be used instead of elongated longitudinal attachment flanges so as not to interfere with the free flow of fresh air from the lower portion 26a of the fresh air supply manifold 26 through the slots 80 and into the manifold portion 2612.

Considering again the fully assembled burner of FIG. 1, the composite gas chamber 36 of the burner bodies 22 of the aligned and interconnecting burners proper 20 is supplied with fuel gas under pressure from one open end thereof and the other end of the composite chamber is closed by a closure plate 100 (see FIG. 6). The closure plate 100 has an outline conforming to the over-all transverse cross-sectional shape of the associated burner body 22 in the flanged end region thereof, and it is provided with bolt holes 102 which register with the similarly disposed bolt holes 52 in the adjacent bolting flanges 50 so that nut and bolt assemblies (not shown) may be employed to hold the closure plate 100 in position.

The other end of the composite gas chamber 36, that is, the end that is supplied with fuel gas under pressure, is provided with an end plate 110 (see FIG. 7) which is similar to the end plate 100 except for the fact that it has in its central portion a threaded circular opening 111 for reception therein of the discharge end of a pipe section 112 which forms a portion of a fuel gas supply line 114.

A control valve 118 in the line 114 is provided for shutoff and fuel gas flow regulation purposes.

Fresh air, i.e., air containing a normal complement of oxygen, is supplied under pressure to the interior of the fresh air supply manifold 26, and specifically to the portion 26a thereof that is rearwards of the burner body 22 as viewed in FIG. 1 by way of a separate air conduit 120 which is connected to and communicates with the discharge side of a motor-driven blower 122, the latter being positioned exteriorly of the duct 12. A pivoted damper 123 is disposed in the conduit 120 near the discharge side of the blower 122. The discharge end of the conduit 120 communicates with the fresh air inlet opening 76 in the wall 74 of the fresh air manifold 26. Means are provided for bleeding a small quantity of air under pressure from the conduit 120 to the gas line 114 for admixture with the incoming fuel gas entering the gas chamber 36 in order to stabilize combustion at extreme burner turndown operation. Such means consist of a by-pass air conduit 124 which extends between the conduit 120 and the gas supply line 114. A check valve 126 is interposed in the by-pass conduit 124 and serves automatically to close the conduit when the pressure of the fuel gas under the control of the valve 118 is increased above the air pressure. Under low fire conditions, the pressure of the fuel gas in the gas supply line 114 is below the pressure of the fresh air in the air conduit 120, and in such an instance, the check valve 126 allows a small amount of air under pressure to be bled from the conduit 120 to the gas supply line 114 so that the flame line along the row of burner gas ports 42 will be continuous and have no blank spots. When the supply of fuel gas is turned up to such a point that there is no possibility of flame extinguishment, the check valve 126 will close automatically and this supply of blower air to the gas supply line will be discontinued.

It is to be noted that during operation of the burner 10 under conditions of extreme turndown, where only a small amount of fuel gas under pressure is admitted through the control valve 118, the flames issuing from the gas burner ports 42 are sustained, at least in part, by the oxygen content of the fresh air under pressure which emanates from the fresh air ports 44 in the flanges 43 of the burner head 40 and conduct fresh air under pressure from the manifold interior portion 26c to the combustion trough 48 at the extreme base of the latter and near the gas ports 42. Additional combustion sustaining oxygen may be derived, as previously described, by the bleeding of fresh air from the conduit 120 to the pipe section 112 and admixture of the air with the fuel gas under pressure in the interior of the burner body. The flame is thus confined principally to the port-equipped region of the burner body at the base of the combustion trough 48 where a thin line of flame may be observed. Under high fire or turn-up conditions, the fresh air outlet ports 82 supply sufficient air near the base of the combustion trough to stabilize combustion.

Upon gradually increasing the amount of fuel gas issuing through the fuel gas supply line 114, the flame will travel forwardly in the combustion trough 48 where it will encounter the fresh air under pressure issuing from the fresh air outlet ports 82. This fresh air creates considerable turbulence in the base or inner region of the trough, as well as in the medial region thereof so that the flame becomes firmly established in these regions of the combustion trough 48 regardless of the oxygen content of the moving gaseous medium within which the burner 10 is disposed.

Under still higher burner turn-up where a relatively large amount of fuel gas under pressure is supplied to the gas chamber 36 in the burner body 22, it is not necessary that a commensurate amount of fresh air under pressure be admitted to the combustion trough 48 through the fresh air outlet ports 82 since there still remains for combustion purposes a supply of oxygen emanating from the gaseous medium which is forced into the chambers 24'through the inlet ports 86 in the rear walls 86 thereof, thus placing the interior of these chambers under moderate pressure and forcing portions of the gaseous medium into the combustion trough '48 through the outlet ports 84. Thus, if the constant supply of fresh air under pressure entering the combustion trough 48 through the outlet ports 82 as heretofore described is completely consumed in the combustion process in the medial region of the trough,

such excess fuel gas as may avoid combustion in this' region and passes forwardly toward the outer or forwardv region of the trough will combine with the oxygen in the gaseous medium under pressure emanating from the outlet ports 84 so that there will always be adequate oxygen to maintain good combustion. Finally, in the event that any unburned fuel gas escapes forwardly from the combustion trough 48, the gaseous medium under pressure which issues forwardly from the outlet ports 88 in the forward walls 60 of the chambers 24 will combine with this unburned fuel gas to assure complete combustion thereof outside or forwardly of the combustion trough, i.e., downstream therefrom.

It will be observed that because the walls 66 of the.

chambers 24 extend at right angles to the stream in the duct 12 and are unobstructedly interposed in the stream, the greater the velocity of the stream, the higher or greater will be the pressure of the gaseous medium in the chambers 24 and, therefore, the higher will be the amount of oxygen that is introduced into the outer region through the outlet ports 84 of the combustion trough 48 for combustion purposes.

From the above description, it will be appreciated that the present gas burner will be found useful in supplying heat to a recirculating air stream of low oxygen content such as is encountered when a high degree of recirculation takes place. Under low fire conditions, the burner operates mainly on pressurized fresh air which is supplied into the base or inner region of the combustion trough, the damper 123 being adjusted to supply adequate air under pressure to the combustion trough through the fresh air ports 44 and the fresh air outlet ports 82 in order to support combustion of all of the fuel gas under pressure issuing from the gas ports 42.

The invention is not to be limited to the exact arrangement of parts shown and described in the accompanying drawings or set forth in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. For example, whereas the present burner is particularly well adapted for use in a recirculating air stream which becomes progressively depleted of its oxygen content during successive cycles, it will be distinctly understood that the burner may, if desired, be used in a fresh air stream for air heating purposes. In addition, the burner may be used in air pollution control work by positioning it in a fume discharge stack leading from an incinerator or a recirculating oven for use in connection with finishing, baking, solvent, evaporation, etc. Whereas the burner has been illustrated and described as being made up of straight burner sections, it is contemplated that the burner may be made to have a round or circular form or configuration. Only insofar as the invention is from said burner face and, in combination with said face, defining a forwardly opening combustion trough, a fresh air manifold completely encompassing said burner body and the rear portions of said flame-confinin g walls, means including the front portions of said walls, defining chambers on opposite sides of the combustion trough and having rear walls which overhang the side portions of the fresh air manifold so as to project unobstructedly into the stream, said fresh air manifold communicating with the rear region of the trough through longitudinal rows of relatively small fresh air ports on opposite sides of and in close proximity to said gas ports, said fresh air manifold also communicating with the rear region of the trough on opposite sides thereof through additional fresh air ports in said rear portions of the flame-confining walls, said chambers communicating with the front region of the combustion trough on opposite side portions thereof through relatively large out let ports in the front portions of said flame-confining walls, said overhanging rear walls of the chambers being formed with gaseous medium inlet ports which expose the interior of said chambers to forced entry of portions of the gaseous medium from said stream, means for regulably supplying fuel gas under pressure to the interior of the burner body, and means for regulably supplying fresh air under pressure to said fresh air manifold.

2. A gas burner as set forth in claim 1 and wherein said chambers are provided with narrow longitudinally extending forward walls having longitudinal rows of additional outlet ports therein.

3. A gas burner adapted for operation in a gaseous 'medium stream of low oxygen content flowing forwardly past the burner, said burner comprising an elongated tubular body having a forward burner face directed downstream and provided with a longitudinal row of closely spaced, relatively small, gas ports in communication with the interior of the body and for producing a forwardly directed flame, a sectional sheet metal shroud secured to said burner body, said shroud including forwardly diverging flame-confining walls which extend forwardly and outwardly from said forward burner face on opposite sidesof the gas ports, and in combination with said burner face, establish a wedge-shaped combustion trough, a box-like enclosure having walls encompassing said burner body and, in combination with the rear portions of said flame-confining walls, establishing a fresh air manifold which completely surrounds the burner body, box-like enclosures disposed on the outer sides of the flame-confining walls and serving, in combination with the front portions of said walls, to establish a pair of laterally displaced chambers, said chambers having rear walls which overhang the opposite sides of the manifold and thus project unobstructedly into the stream, the interior of said fresh air manifold communicating with the rear region of said combustion trough through longitudinal rows of relatively small fresh air ports on opposite sides and in close proximity to said row of gas ports, said fresh air manifold also communicating with the rear region of the combustion trough on opposite sides thereof through additional and relatively large fresh air ports which are formed in said rear portions of the flame-confining walls, said chambers communicating with the front region of the combustion trough on opposite side portions thereof through relatively large outlet ports in the front portions of said flame-confining walls, said overhanging rear walls of the chambers being formed with a plurality of inlet ports which expose the interior of said chambers to forced entry of portions of the gaseous'medium from said stream, means for regulably supplying fuel gas under pressure to the interior of said burner body, and means for regulably supplying fresh air under pressure to said fresh air manifold.

4. A gas mixing burner as set forth in claim 3 and wherein the chambers are provided with narrow longitudinally extending forward walls having longitudinal rows of additional outlet ports therein.

5. A gas burner adapted for operation in a moving stream of a gaseous medium flowing forwardly past the burner, said burner comprising an elongated tubular burner body presenting a forward burner face directed downstream and provided with a longitudinal row of small gas ports therein in communication with the interior of the body for producing a forwardly directed flame, flame-confining walls extending forwardly from said burner face and, in combination with said face, defining a forwardly opening combustion trough, a fresh air manifold completely encompassing said burner body and the rear portions of said flame-confining walls, said fresh air manifold communicating with the rear region of the trough through longitudinal rows of relatively small fresh air ports on opposite sides of and in close proximity to said gas ports, said fresh air manifold also communicating with the rear region of the trough on opposite sides thereof through additional fresh air ports in said rear regions of the flame-confining walls, the front portions of said flame-confining walls being in communication with said moving stream of gaseous medium and having formed therein relatively arge ports for permit ting a portion of the stream to flow therethrough into the front region of the trough, means for regulably supplying fuel gas under pressure to the interior of the burner body, and means for regulably supplying fresh air under pressure to said fresh air manifold.

References Cited UNITED STATES PATENTS 3,051,464 8/1962 Yeo et 211. 3,265,376 8/ 1966 Spielman. 3,437,322 4/1969 Flynn.

EDWARD G. FAVORS, Primary Examiner US. Cl. X.R. 263-l9 

